All too often over the past century, when repressive governments have committed egregious acts, the rest of the world — because of ignorance, fear or greed — has simply shrugged.

China’s treatment of its ethnic Uighur population and other Muslim minority groups should not be allowed to become one of those moments.

In the past month, the US congressional-executive commission on China and a UN committee on racial discrimination have both cited “numerous and credible reports” that as many as 1m Uighurs and other Chinese Muslims are being held in extrajudicial prison camps in the western province of Xinjiang. The UN says another 2m — roughly 20 per cent of the entire Uighur population — may have been forced into “re-education camps for political and cultural indoctrination”, where they are made to renounce Islam and praise the Communist party and President Xi Jinping.

Numerous reports have emerged of torture, medical neglect and abuse as well as deaths of some detainees in the camps. Jerome Cohen, a law professor and expert on Chinese human rights, has said the last time so many people were detained outside the formal criminal process in China was in the “anti-rightest” campaign of the late 1950s. That saw the first use of China’s “re-education through labour” gulags.

Yet most governments have declined to criticise Beijing or even ask for more transparency about the situation in Xinjiang. Even many predominantly Muslim countries have remained silent, including Turkey, which shares deep ethnic, cultural and linguistic roots with the Uighur people.

In spite of overwhelming evidence from news reports, human rights groups and Uighur exiles, the Chinese government has stuck to a policy of almost total denial. It describes the sprawling network of camps as “vocational education and employment training centres”, and insists “the people of all ethnic groups in Xinjiang cherish their happy and peaceful life”.

Chinese state media have lauded the measures as necessary to save the region from “massive turmoil” and from becoming “China’s Syria”.

Sporadic terrorist attacks have been carried out by alleged Uighur Islamic extremists in China in recent years. It is true that none has been reported since repression was ramped up in the region. But China’s leaders would be wise to realise that the treatment of the Uighurs is likely to nurture a far greater terrorist threat in the future.

It is also possible that the scale of the abuse in the region has been exaggerated in the vacuum created by Beijing’s denials. If so, China’s leaders have every incentive to allow open and unfettered access to the region for foreign diplomats and the world’s media. To address concerns raised by the UN committee, Beijing should allow the UN rapporteur on the issue to visit. If not, other countries should hold it to account under international treaties.

The sheer size of China’s market makes foreign states all too willing to overlook alleged human rights abuses. But if governments will not act, there is more the corporate sector could do. Without transparency from Beijing, western companies should at least decline to supply China’s security services, and to do business in Xinjiang.

The region is also the centrepiece of Mr Xi’s signature Belt and Road Initiative to connect Asia and Europe and promote Chinese trade. In theory, that provides international partners with considerable leverage. Countries should not sign unless they receive credible promises that Beijing will end systematic and brutal oppression in Xinjiang.